sched/fair: Avoid calling sync_entity_load_avg() unnecessarily

Call sync_entity_load_avg() directly from find_idlest_cpu() instead of
select_task_rq_fair(), as that's where we need to use task's utilization
value. And call sync_entity_load_avg() only after making sure sched
domain spans over one of the allowed CPUs for the task.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: http://lkml.kernel.org/r/cd019d1753824c81130eae7b43e2bbcec47cc1ad.1524738578.git.viresh.kumar@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 7 insertions, 9 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4b346f358005..1f6a23a5b451 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6199,6 +6199,13 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p
         if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
                 return prev_cpu;
 
+        /*
+         * We need task's util for capacity_spare_wake, sync it up to prev_cpu's
+         * last_update_time.
+         */
+        if (!(sd_flag & SD_BALANCE_FORK))
+                sync_entity_load_avg(&p->se);
+
         while (sd) {
                 struct sched_group *group;
                 struct sched_domain *tmp;
@@ -6651,15 +6658,6 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
 
         if (unlikely(sd)) {
                 /* Slow path */
-
-                /*
-                 * We're going to need the task's util for capacity_spare_wake
-                 * in find_idlest_group. Sync it up to prev_cpu's
-                 * last_update_time.
-                 */
-                if (!(sd_flag & SD_BALANCE_FORK))
-                        sync_entity_load_avg(&p->se);
-
                 new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
         } else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
                 /* Fast path */